stief - you are obviously much cleverer than I am - I am just old and stupid. Needless to say, having had a think, by typing .dat into the finder I discovered that there are such files in my mac.

Having followed your suggestion and typed "pop-up" into the search facility in this forum I find that my original question is well covered. Thanks again.
Yesterday I purchased the Pro version of Limewire and so hope that the pop-ups will disappear.

I wonder if the nos. at the top of the window are for a FTP request? I do not intend to find out!

Regards.